Summary:
Added stream interecptor which gets a chance to augment the messages off the wire. Stream interceptor transformations are async and can fail due to network errors so added error state with a retry button. The retry button will just call the function again.
I am also handling errors better generally when this method fails unexpectedly, logging more clearly what went wrong and communicating it to the user
Did some refactoring of subtree update event to support this
Reviewed By: lblasa
Differential Revision: D44415260
fbshipit-source-id: a5a5542b318775b641d53941808399a8fa4634d3
